sicp.clj

(ns sqrt)
(defn abs [n]
(if (< n 0)
  (* -1 n)n))


(defn goodenough? [guess prevguess]
 (> 0.0000001 ( abs (- guess  prevguess) ) ))


(defn sqrt-approximation [x y]
  ( / (+ y (/ x y)) 2.0))

(defn cubert-approximation [x y]
 (/ (+ (/ x (Math/pow y 2)) (* 2 y))3) )

(defn root 
  ([ approximation x ] (root x 1 0 approximation) )
  (  [x guess prevguess approximation]
    ( if (goodenough? guess prevguess )
      guess
      ( recur x (approximation x guess)  guess approximation))))

(def sqrt (partial root sqrt-approximation  ))
(def cubert (partial root cubert-approximation  ))